मृदम्भसा by clay and water यथा just as भित्तिः a wall निर्मिता is built वै indeed मृदम्भसा by clay and water
आप्यायते abounds in size तथा even so भुक्तैः by the consumed भूतैः elements देहादयः body, etc. अपि also च too

When water is added to clay and a wall is built, we see that the increase in the quantity of the mixture results in the increase of the thickness of the wall. The increase in size, bulging, by intake of food is known from perceiving the body aggregate. That is why the creation of the body aggregate is stated to be by food, etc. When sufficient food is taken in there is growth and maintenance of the body aggregate. In the absence of intake, one can easily perceive the decay or decrease in the parameters of the body aggregate.

Since the body-mind complex is a product of the elements, a discriminating person should give up the identification with the inert entity and claim his identity with his true self that is consciousness and the witness of the inert world of body, objects of desire, etc. It is quite natural, without being taught by anyone, for a person to take the body-mind complex to be the self. It is this error that is called aham-adhyāsa, the superimposition of the ‘I’ in the body, etc. It is this adhyāsa that leads to mama-adhyāsa, identification with what is considered as ‘mine’, that is samsāra, bondage. The remedy to this situation is to give up the ‘I’ identification with the not-self and realize oneself as the Self that is the witness of the entire gamut of not-self consisting of the body-mind and the external world of objects. While the body-mind complex is a group of manifoldness, the Self is singular, unitary. Manifoldness is the product of māyā, prakṛti and unitariness is not a product at all; it is Consciousness, never produced and never destroyed. It is the aim of the Veda to bring the aspirant to the discriminative insight where he gives up his identification with the inert body-mind and realizes his true identity as the Self, the Ātman, verily Consciousness.

The mind-body complex of living beings is certainly quite distinct from the elements. How then can there be a cause-effect relationship between the elements and the mind, body, etc.?

The passage from the Chāndogya Upaniṣad (6.6.1) दध्नः सोम्य मथ्यमानस्य योऽणिमा स ऊर्ध्वः समुदीषति तत्सर्पिर्भवति [‘From curds, O dear, upon churning, emerges its subtle content which becomes clarified butter (ghee)’] gives the analogy of ghee, the effect, emerging from the curds, the cause, owing to the act of churning. At first sight, it would be difficult to appreciate the cause-effect relationship here. This is because the ghee and the curds are quite distinct from each other. Yet, upon analyzing the phenomenon, one can clearly know that the process of churning brings out the subtle, unseen, ghee (through the butter that is first extracted). The analogy is to explain the transformation of the elements – fire, water and earth – through the process of cooking in the fire of the stomach, into body, the sense / motor organs, the mind and intellect. The idea is that food consumed has the elements in it and upon their being processed within the stomach, the body, organs, mind, etc. are nourished. In the absence of food the body, etc. emaciate and finally die. The sustenance of the body metabolism is dependent on food that is itself a transformation of the elements.

By the analogy of curds-ghee the Upaniṣad establishes that the body aggregate is the product of elements, bhautikam. The unmistakable message thus conveyed is that an aspirant after truth has to shift his identification with the body, etc. on to the Self, the Ātman, the Consciousness. It is only the erroneous identification, nay, admixture, of the conscious self with the inert object that brings forth the phenomenon of samsāra, bondage. The Consciousness, Ātman, is caught up, as it were, in the cage of the body-mind complex. The afflictions of the material body, mind etc. are wrongly taken to be of the Self and so continues the transmigratory life. The end to such a perpetual samsāra comes with the discriminating insight that the Self is ever separate from the body aggregate. Once this occurs and firms up, there will be no seed of ignorance that can sprout into the next embodied life. It is freedom from embodied life that is called mokṣa, liberation. The avowed object of the Veda is to enable the human to attain this.

Let the organ of speech and the prāṇa be effects of food (through the elements), why should one hold the mind to be an effect too? After all, the vaiśeṣika doctrine holds the mind to be an eternal entity. When the aspirant-son Śvetaketu questioned his preceptor-father Uddālaka on this and pleaded for further explanation, the father compassionately subjected the boy to a physical test with the intention of demonstrating his point: षोडशकलः सोम्य पुरुषः पञ्चदशाहानि माशीः काममपः पिबापोमयः प्राणो नपिबतो विच्छेत्स्यत इति (6.7.1) [“A person, my dear, consists of sixteen parts. Do not eat any food for fifteen days, but drink as much water as you like. Since the prāṇa consists of water, it will not be cut off if you drink water.”]

When the boy refrained from eating food for fifteen days, the mind faculty weakened due to which he could not recall the Veda that he had memorized. Upon resuming intake of food, the mind grew in strength and he could recollect what he had committed to memory. From this it became clear that food has its effect on the mind’s faculties. The word ‘buddhi’ (intellect) is considered non-different from ‘manas’ (mind).

What was said earlier with regard to the gross body (in verse 69) that it is the non-Ātman is applicable here, in the case of the mind as well. Just as one should repose identity in his true Self, the Consciousness, since the body is not the self, so too one has to repeatedly disassociate from the mind/intellect, since it is not the self, and fix one’s identity in the true self, the consciousness that is the witness of the mind and the body. In fact the very first verse of the 13th chapter of the Bhagavadgītā is this lesson: The body, etc. is the object to the Consciousness that is the witness, knower, of it. The seer-seen distinction helps the aspirant to learn to claim his true self, the conscious witness, and disown the inert witnessed body-mind world of duality. A firm conviction in this discrimination, says the very 13th chapter of the Bhagavdgītā, at the end, leads to liberation.